This invention relates generally to needle roller bearings and, more particularly, to needle roller bearings used in the conversion of rotary motion into reciprocating linear motion.
It is not uncommon for bearings, especially needle roller bearings, to be used in the conversion of rotary motion, as might be created by a motor, into linear motion of another member, for example, a hydraulic piston actuating an anti-lock brake system. In such applications, the bearing provides a cam surface and the pistons serve as cam followers. To provide the required camming action, the bearings are mounted on either an eccentric shaft or an eccentric sleeve mounted on a cylindrical shaft.
In the case where the bearing is supplied on an eccentric sleeve which is made of powder metal, restraining the bearing to prevent axial play is a particularly difficult problem. Because of limited manufacturing tolerances of powder metal and stack-up of such tolerances, it is generally possible to mount the bearing onto the eccentric sleeve only by means of a slip-fit. The slip-fit is considerably "looser" than a press-fit and does not provide sufficient axial restraint of the bearing.
Apart from the problem of axially restraining a slip-fitted bearing, there is also a problem of rotational, or dynamic, balance when the bearing is slip-fitted onto an eccentric sleeve which is itself press-fitted onto a rotatable shaft. Unless the masses are properly balanced, rotation of the eccentrically mounted bearing will create a rotationally unbalanced load which may lead to premature failure of the bearing. Present bearing and eccentric sleeve combinations have been difficult to balance adequately.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.